Pingbacks - let you know your post has been linked to by another LJ user. Only works if both of you have opted in.
Twitter/facebook - you can crosspost (posts and comments). You have to opt in and can either default to always crosspost or can select on a post by post basis. Commenters can opt to crosspost their comments.
Facebook connect - you can access LJ using your Facebook ID just like LJ users on DW
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Pingbacks - let you know your post has been linked to by another LJ user. Only works if both of you have opted in.
Twitter/facebook - you can crosspost (posts and comments). You have to opt in and can either default to always crosspost or can select on a post by post basis. Commenters can opt to crosspost their comments.
Facebook connect - you can access LJ using your Facebook ID just like LJ users on DW